The insulin responsiveness of neutrophils, lymphocytes, and macrophages will be assessed using cells from insulin-deficient animals. The ability of streptozotocin-diabetic animals to inhibit the growth of tumor cells in vivo will be measured. In vitro studies of insulin effects on glucose uptake and glucose oxidation will be evaluated using thymus-dependent lymphocytes and macrophages from diabetic as well as normal mice. Drug- and hormone-induced changes in cyclic AMP and cyclic GMP accumulation will be examined for leukocytes from normal and diabetic mice. An evaluation of insulin effects on continuous macrophage cell lines will be assessed. Measurements of glucose oxidation, glucose uptake, and glucosamine incorporation will be done on macrophages incubated with agents known to enhance tumor cell cytotoxicity. Changes in cyclic AMP and cyclic GMP levels will be evaluated to explain the effects of insulin and activating agents on macrophages. Neutrophils from the peripheral blood of diabetic patients will be studied for insulin effects on cyclic AMP and cyclic GMP accumulation. Normal and diabetic PMNs will be used to compare in vitro effects of insulin on chemiluminescence, chemotaxis, and cyclic nucleotide levels.